The present invention relates to the automatic setting of an operation mode of an air conditioner which is capable of a cooling operation, a heating operation and a dehumidifying or drying operation.
In order to realize automatic setting of an operation mode, it has been proposed to automatically set a cooling operation or a heating operation according to whether a room temperature or an outdoor temperature is higher or lower than a set value. However, none of the prior art devices has yet to succeed in realizing optimum settings during an intermediate or transitional period of the four seasons of a year.
An attempt has been made to overcome the problems encountered to the prior art devices described above, as disclosed in Japanese Patent Publication No. 63-150550/1988 (unexamined), in which a plurality of temperature zones A to L are set by using a plurality of room-temperature set values and a plurality of outdoor-temperature set values freely and, for example, temperature zone A is assigned to a zone for setting a heating operation, temperatures K, G and H are assigned to a zone for setting a dehumidifying (or drying) operation, a temperature zone L is assigned to a zone for setting a cooling operation, and the other zones are assigned to a supervising zone which is a zone for detecting a room temperature at predetermined time intervals. In this prior art, any one of these temperature zones is determined to be the most suitable one according to a room temperature and an outdoor temperature, and a desired operation mode is automatically selected on the basis of this result of the determination.
Japanese Patent Publication No. 63-306344/1988 (unexamined) shows a device for determining any one of the four seasons by using room temperature and date information. The determination of a season is normally made on the basis of the date information, and during a transitional period (that is, a period having unstable conditions corresponding to a plurality of seasons in which temperature conditions are not stable), the determination of a season is made by measuring the maximum and minimum temperatures of the day.
However, in any of the prior art devices described above, it is difficult to achieve accurate selection during an intermediate period, such as spring and autumn, if automatic selection is executed from among the cooling operation, heating operation and dehumidifying operation.
When a plurality of temperature zones are set and automatic selection of an operation is executed, a problem arises in that the temperature sensation (or feeling) of a user varies depending on spring or autumn even within the same temperature zone. More specifically, users generally feel cold in spring and desire heating, but in autumn, feel hot and desire cooling, even when the same temperature zone is selected in spring and autumn. It is, therefore, quite difficult to realize an optimum automatic selection merely by the setting of temperature zones.
Another problem arises in that if a determination of a season is made, the result of the determination does not always correspond to a desired operation mode and, particularly in summer, it is difficult to determine an accurate timing at which switching from the dehumidifying operation is to be executed to the cooling operation.